One of the most important aspects of surgery is the control of bleeding. Existing electrocoagulation devices are ubiquitous, but are ineffective for attaining hemostasis in highly vascularized tissues such as the liver and spleen. We have demonstrated that high-intensity ultrasound can be successfully used to terminate bleeding in both damaged blood vessels as well as gross damage to the capillary bed. We propose to develop a medical device that would use low-intensity diagnostic ultrasound to identify areas and/or specific sites of bleeding, and high-intensity focused ultrasound to induce hemostasis. In this Phase I research, we propose to develop an important initial component of the eventual commercial device; viz., a multi-element ultrasound transducer array, and its associated control system, that can be used for both imaging and therapy. In addition, we propose to test the capability of our Therastat System to induce acoustic hemostasis in an animal model. Successful accomplishment of the goals of the Phase I study would permit us to develop an engineering prototype for animal and human feasibility studies in a Phase II effort. PROPOSED COMMERCIAL APPLICATION: Existing electrocautery devices have limited use for surgery of major organs such as the liver and spleen. It is also difficult to perform endoscopic suturing to control bleeding in minimally invasive surgery. We propose to construct an ultrasound image-guided acoustic hemostasis device that would have widespread applications in open and minimally invasive surgery, and in trauma care.